DE102019109226A1 - Separator for lithium metal-based batteries - Google Patents

Abstract

A modified separator for a high-energy lithium metal-based electrochemical cell and associated manufacturing methods are provided. The modified separator includes a substrate with a dopant and a cap layer disposed on the doped substrate. The dopant and the compound comprising the cap layer are independently selected from the group consisting of: alumina (AlO), titania (TiO), zirconia (ZrO), zinc oxide (ZnO), iron oxide (FeO), tin oxide (SnO) , Silica (SiO), tantalum oxide (TaO), lanthanum oxide (LaO), hydrofluoroolefin (HfO), cerium oxide (CeO), and combinations thereof.

Description

INTRODUCTION

This section provides background information related to the present disclosure, which is not necessarily prior art.

The present disclosure relates to lithium metal-based electrochemical cells comprising doped and coated separators and high-viscosity electrolytes, and to methods of production in combination therewith.

Against this background, high energy density electrochemical cells, such as lithium-ion batteries and lithium-sulfur batteries, can be used in a variety of consumer products and vehicles, such as hybrid electric vehicles (HEV) and electric vehicles (EV). Typical lithium-ion and lithium-sulfur batteries include a first electrode, a second electrode, an electrolyte material, and a separator. One electrode serves as a positive electrode or cathode (on discharge) and another serves as a negative electrode or anode (on discharge). A stack of battery cells may be electrically connected to increase overall performance. Conventional rechargeable lithium-ion batteries operate by reversibly forwarding and diverting lithium ions between the negative electrode and the positive electrode and back again. A separator and an electrolyte are disposed between the negative electrode and the positive electrode. The electrolyte is suitable for the conduction of lithium ions and can be in solid (eg solid state diffusion) or liquid form. When charging the battery, lithium ions move from a cathode (positive electrode) to an anode (negative electrode) and when discharging the battery in the opposite direction.

Many different materials can be used to make components for a lithium-ion battery. Common materials for negative electrodes include lithium insertion materials or alloy host materials such as lithium graphite intercalation compounds or lithium-silicon compounds, lithium-tin alloys, and lithium titanate (LTO) (eg, Li _{4 + x} Ti ₅ O ₁₂ where 0 ≤ x ≤ 3, such as Li ₄ Ti ₅ O ₁₂ ). The negative electrode may also be made of metallic lithium (often referred to as a lithium metal anode (LMA)), whereby the electrochemical cell is considered a lithium metal battery or cell. The use of metallic lithium in the negative electrode of a rechargeable battery has several potential advantages, including the highest theoretical capacity and the lowest electrochemical potential. For example, batteries with lithium-metal anodes can have a higher energy density, potentially doubling storage capacity and halving the size of the battery while maintaining a similar lifetime to other lithium-ion batteries. Lithium metal batteries are thus one of the most promising candidates for high energy storage systems.

However, in some cases, lithium metal batteries also have potential disadvantages. For example, the comparatively high reactivity of the lithium metal can lead to interfacial instability and undesirable side reactions. During the manufacture and / or operation of the electrochemical cell, side reactions may occur between the lithium metal and various species to which the lithium metal may be exposed. These side reactions can lead to unfavorable dendritic formation. Furthermore, polyolefin-based separators, such as may be used in lithium-metal batteries, exhibit, in certain aspects, a generally low wettability to electrolytes. In this case, the electrolyte can not penetrate the separator or completely fill the pores of the porous separator, resulting in reduced performance and life of the lithium metal battery. Accordingly, it would be desirable to develop reliable, high performance materials, such as comparatively high wettability separators, for use in high energy electrochemical cells and related processes that minimize or prevent dendrite formation.

SUMMARY

This section provides a general summary of the disclosure and is not a comprehensive disclosure of the full scope or all features.

In various aspects, the present disclosure provides a modified separator for an electrochemical cell that circulates lithium ions. The modified separator may include a polymeric separator and an electrolyte system having a viscosity ranging from about 50 mPa.s to about 500 mPa.s. The polymeric separator may comprise a doped substrate and a cover layer disposed thereon. The substrate may be doped with a dopant selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tin oxide (SnO), silicon oxide (SiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), hydrofluoroolefin (HfO), cerium oxide (CeO ₂ ), and combinations thereof. The cover layer may be one of a polymer coating and a ceramic one Be metal oxide coating. The ceramic metal oxide layer may include at least one of the dopants.

In one aspect, the capping layer may have a thickness in the range of about 1 nm to about 50 μm.

In one aspect, the polymeric cover layer may include one of an aluminum oxide composite (Alukon) film, a zirconium alkoxide composite (zirconium) film, a titanium alkoxide composite (Titanicon) film, and a polyimide film.

In one aspect, the polymeric overcoat layer may include an alumina composite (Alukon) film comprising a precursor material selected from the group consisting of: trimethylaluminum (TMA), ethylene glycol (EG), terephthaloyl chloride (TC), glycidol ( GLY), hydroquinone (HQ) and combinations thereof.

In one aspect, the electrolyte system may be one of an ether-based electrolyte system and a carbonate-based electrolyte system.

In one aspect, the modified separator may have a melting point in the range of about 120 ° C to about 200 ° C, and the precursor material for the alumina composite (Alukon) film of the polymeric topcoat may be a combination of trimethylaluminum (TMA) and ethylene glycol (EC).

In one aspect, the polymeric coating may be a molecular layer deposition (MLD) capping layer.

In one aspect, the ceramic-like metal oxide cap layer may include a ceramic material selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), silica (SiO ₂ ) and combinations thereof.

In one aspect, the ceramic metal oxide coating may be an atomic layer deposition (ALD) capping layer.

In one aspect, the substrate may include an amount of dopant in the range of about 1 g / m ² to about 10 g / m ² .

In one aspect, the substrate may include a polyolefin.

In one aspect, the electrolyte system may include a lithium salt selected from the group consisting of: lithium hexafluorophosphate (LiPF ₆ ), lithium bis (fluorosulfonyl) imide (LiN (FSO ₂ ) ₂ ) (LiSFI), lithium bis (oxalato) borate (LiB ( C ₂ O ₄ ) ₂ ) (LiBOB), lithium difluorooxalatoborate (LiBF ₂ (C ₂ O ₄ )), lithium perchlorate (LiClO ₄ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN ), Lithium tetrafluoroborate (LiBF ₄ ), lithium tetraphenylborate (LiB (C ₆ H ₅ ) ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), bis (trifluoromethane) sulfonimidic lithium salt (LiN (CF ₃ SO ₂ ) ₂ ) and combinations; and a solvent selected from the group consisting of: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, Methyl propionate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and combinations thereof.

In various aspects, the present disclosure provides a high-energy lithium metal-based electrochemical cell including a polymeric separator and an electrode having a lithium metal-based electroactive material and having surfaces that are substantially free of dendrite formations. The polymeric separator may include a substrate comprising a dopant and a cap layer disposed on the doped substrate. The dopant and the compound comprising the capping layer may each be independently selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), iron oxide ( Fe ₂ O ₃ ), tin oxide (SnO), silicon oxide (SiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), hydrofluoroolefin (HfO), cerium oxide (CeO ₂ ) and combinations thereof. The cover layer may have a thickness in the range of about 1 nm to about 10 μm.

In one aspect, the high-energy lithium metal-based electrochemical cell may further include an electrolyte system having a viscosity in the range of about 50 mPa.s to about 500 mPa.s. The electrolyte system may include a lithium salt dissolved in an organic solvent, wherein the lithium salt has a concentration in the electrolyte system in the range of about 2 M to about 5 M.

In one aspect, the substrate may include a polyolefin selected from the group consisting of: polyethylene (PE), polypropylene (PP), and combinations thereof.

In one aspect, the substrate may include about 2 g / m ² to about 5 g / m ^{2 of} the dopant.

In still other aspects, the present disclosure provides a method of manufacture of a coated separator. The method may include applying one of a polymeric capping layer and a ceramic metal oxide capping layer to a doped separator having a sheet shape. The doped separator may include a dopant selected from the group consisting of: alumina (Al ₂ O ₃ ); Titanium dioxide (TiO ₂ ); Zirconium dioxide (ZrO ₂ ); Zinc oxide (ZnO); Iron oxide (Fe ₂ O ₃ ), tin oxide (SnO); Silicon oxide (SiO ₂ ); Tantalum oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), hydrofluoroolefin (HfO), cerium oxide (CeO ₂ ) and combinations thereof.

In one aspect, the overcoat layer may have a thickness of about 1 nm to about 50 nm, and the coated separator may further include an electrolyte system having a viscosity of about 50 mPas to about 500 mPas.

In one aspect, the ceramic-like metal oxide cap layer may include a ceramic material selected from the group consisting of: alumina (Al ₂ O ₃ ); Titanium dioxide (TiO ₂ ); Zirconium dioxide (ZrO ₂ ); Zinc oxide (ZnO); Silicon oxide (SiO ₂ ); and combinations thereof, and may be disposed on the doped separator by atomic layer deposition (ALD).

In one aspect, the polymeric capping layer may include one of an alumina composite (alukon) film, a zirconium alkoxide composite (zirconium) film, a titanium alkoxide composite (titanicon) film, and a polyimide film, and may be supported on the doped separator by molecular layer deposition (MLD). to be ordered.

In one aspect, the polymeric overcoat layer may be an Alconic film and the precursor material is selected from the group consisting of: trimethylaluminum (TMA), ethylene glycol (EG), terephthaloyl chloride (TC), glycidol (GLY), hydroquinone (HQ), and combinations thereof.

Other applications will be apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

list of figures

• 1 ist ein Schaubild einer exemplarischen elektrochemischen Batterie zum Zwecke der Veranschaulichung;
• 2 ist eine Schnittansicht eines exemplarischen beschichteten Separators, der gemäß bestimmten Aspekten der vorliegenden Offenbarung gebildet wurde; und
• 3 ist eine grafische Darstellung der Kapazitätserhaltung pro Zyklus von vergleichenden elektrochemischen Zellen, die jeweils ein Elektrolytsystem mit einer Viskosität im Bereich von etwa 50 mPa·s bis etwa 500 mPa·s und einen Separator auf Polypropylenbasis umfassen.

The drawings described herein are for illustrative purposes only of selected embodiments and are not all the possible implementations and are not intended to limit the scope of the present disclosure.

• 1 FIG. 12 is a diagram of an exemplary electrochemical battery for purposes of illustration; FIG.
• 2 FIG. 4 is a sectional view of an exemplary coated separator formed in accordance with certain aspects of the present disclosure; FIG. and
• 3 Figure 4 is a graph of per-cycle capacity retention of comparative electrochemical cells each comprising an electrolyte system having a viscosity ranging from about 50 mPa.s to about 500 mPa.s and a polypropylene-based separator.

Like reference characters in the several views of the drawings indicate similar parts.

DETAILED DESCRIPTION

Exemplary embodiments are provided so that this disclosure will be thorough and fully convey the scope of those skilled in the art. Numerous specific details are set forth, such as examples of specific compositions, components, devices and methods described to provide a thorough understanding of embodiments of the present disclosure. Those skilled in the art will recognize that specific details may not be required, that exemplary embodiments may be embodied in many different forms, and that neither of the embodiments is to be construed to limit the scope of the disclosure. In some exemplary embodiments, well-known methods, well-known device structures, and well-known techniques are not described in detail.

The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting in any way. As used herein, the singular forms "a" and "the" may also include plurals, unless the context clearly precludes this. The terms "comprising,""comprising,""including," and "comprising" are inclusive, and therefore, indicate the presence of the specified features, elements, compositions, steps, integers, acts, and / or components, but do not preclude the existence of or adding one or more other features, integers, steps, acts, elements, components, and / or groups thereof. Although the term "comprising" as open-ended is to be understood as a non-limiting term used to describe and claim various of the following Alternatively, the term may alternatively be understood as meaning, for example, instead of being a more limiting and restrictive term such as "consisting of" or "consisting essentially of". Thus, any embodiment that presents compositions, materials, components, elements, functions, integers, operations, and / or method steps, expressly includes embodiments of the present disclosure consisting of, or consisting essentially of, compositions, materials, components, Elements, functions, numbers, operations and / or process steps. By "consisting of", the alternative embodiment excludes any additional compositions, materials, components, elements, functions, numbers, operations, and / or operations, while "consisting essentially of" excludes any additional compositions, materials, components, elements, functions , Numbers, operations and / or process steps, which materially affect the fundamental and novel properties are excluded from such an embodiment, but any compositions, materials, components, elements, functions, integers, operations and / or process steps, the material not the may affect basic and novel characteristics may be included in the embodiment.

All of the method steps, processes, and operations described herein are not to be construed as necessarily requiring the order described or illustrated, unless specifically stated as the order of execution. It should also be understood that additional or alternative steps may be used unless otherwise stated.

When a component, element, or layer is described as "on," "in, engaged," "connected to," or "coupled to," another component or layer, it may are either directly on / on the other component, the other element, or the other layer, in engagement with, connected to, or coupled to, or there may be intervening elements or layers. In contrast, when an element is described as being "directly on," "directly engaged with," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or elements Layers be present. Other words used to describe the relationship between elements are equally understood (eg, "between" and "directly between," "adjacent" and "directly adjacent," etc.). As used herein, the term "and / or" includes all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc., may be used herein to describe various steps, elements, components, regions, layers, and / or sections, these steps, elements, components, regions, layers, and / or sections are not intended to be these expressions are restricted. These terms are only used to distinguish one step, item, component, region, layer, or section from another step, another element, another region, another layer, or another section. Terms such as "first," "second," and other numerical terms, as used herein, do not imply any sequence or order unless clearly indicated by the context. Thus, a first step discussed below, a discussed first element, a discussed component, a discussed region, a discussed layer, or a discussed section could be referred to as a second step, a second element, a second component, a second region, a second layer, or a second region. without deviating from the teachings of the exemplary embodiments.

Spatial or time related terms, such as "before", "after", "inner", "outer", "below", "below", "lower", "above", "upper", and the like, may be used herein to better describe Relationship of an element or a property to other element (s) or property (s), as shown in the figures, are used. Spatial or time related terms may be intended to rewrite various device or system deployments in use or in operation, in addition to the orientation shown in the figures.

In this disclosure, the numerical values basically represent approximate measurements or limits of ranges, such as minor deviations from the particular values and embodiments having approximately that value, as well as those having exactly that value. In contrast to the application examples provided at the end of the detailed description, all numerical values of the parameters (eg, sizes or conditions) in this specification, including the appended claims, are to be understood in all instances by the term "about," whether or not "Approximately" actually appears before the numerical value. "Approximately" indicates that the numerical value disclosed allows for some inaccuracy (with a certain approximation to accuracy in the value, approximately or realistically close to the value, approximate). If the inaccuracy provided by "about" is not otherwise understood by those of ordinary skill in the art to be ordinary, then "about" as used herein will at least indicate variations resulting from ordinary measurement techniques and the use of such parameters. For example, "about" may be a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less may be equal to or less than 0.5% and may, under certain aspects, be less than or equal to 0.1%. In addition, specifying ranges includes specifying all values and subdivided ranges within the entire range, including the endpoints and subdomains specified for the ranges.

The present disclosure provides a modified separator for a high-energy lithium-metal based electrochemical cell, and corresponding methods for making the same. The modified separator comprises a doped substrate and a cover layer disposed thereon. In various cases, the substrate comprises a dopant selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tin oxide (SnO), silicon oxide (SiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), hydrofluoroolefin (HfO), cerium oxide (CeO ₂ ), and combinations thereof. The cover layer may be one of a polymer and a ceramic metal oxide. The polymeric topcoat may be a molecular layer deposition (MLD) topcoat comprising a film of an alumina composite (Alukon) film, a zirconium alkoxide composite (zirconium) film, a titanium alkoxide composite (Titanicon) film and a polyimide film. The ceramic metal oxide coating may be an atomic layer deposition (ALD) cladding layer comprising a ceramic material selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide ( ZnO), silica (SiO ₂ ) and combinations thereof. In various instances, the capping layer may have a thickness in the range of about 1 nm to about 50 nm, optionally from about 1 nm to about 10 nm, and in certain aspects, optionally from about 2 nm to about 10 nm. The modified separator may include an electrolyte having a viscosity in the range of about 50 mPa.s to about 500 mPa.s. The modified separator may have a wettability to the electrolyte exhibited by a comparatively small contact angle. The contact angle may range from about 10 degrees to about 40 degrees.

An exemplary and schematic representation of a battery 20 , which performs lithium-ion cycles, is in 1 shown. The battery 20 may be a lithium ion electrochemical cell, a lithium sulfur electrochemical cell or a lithium selenium battery, each having a negative electrode 22 , a positive electrode 24 and one between the two electrodes 22 . 24 arranged porous separator 26 includes. The separator 26 includes an electrolyte system 30 that also in the negative electrode 22 and the positive electrode 24 may be included. A negative electrode current collector 32 can be at or near the negative electrode 22 be arranged and a positive electrode current collector 34 can be at or near the positive electrode 24 be positioned. The negative electrode current collector 32 and the positive electrode current collector 34 each pick up the electrons and transport the free electrons to and from an external circuit 40 path. An interruptible external circuit 40 and consumer device 42 connects the negative electrode 22 (via their current collector 32 ) and the positive electrode 24 (via their current collector 34 ).

The porous separator 26 , which serves as both an electrical insulator and mechanical support, is between the negative electrode 22 and the positive electrode 24 inserted to prevent physical contact, thereby preventing the occurrence of a short circuit. In addition to providing a physical barrier between the two electrodes 22 . 24 can the porous separator 26 a minimum resistance path for the internal passage of the lithium ions (and associated anions) during the lithium ion cycle, to aid in the functioning of the battery 20 provide. In lithium-ion batteries, lithium and / or alloys intercalate into the active electrode materials. However, in a lithium-sulfur battery or a lithium-selenium battery, instead of deposits or alloys, the lithium dissolves from the negative electrode and travels to the positive electrode, thereby reacting / discharging during discharge while it is being charged the negative electrode is located.

The battery 20 can be done by connecting an external power source to the battery 20 To reverse the electroactive reactions of the battery discharge recharged and harnessed at any time. The connection of an external power source to the battery 20 forces the generation of electrons and the release of lithium ions from the positive electrode 24 , The electrons passing through the external circuit 40 back to the negative electrode 22 flow and the lithium ions passing through the electrolyte 30 through the separator 26 back to the negative electrode 22 be transported, connect again to the negative electrode 22 and refill them with lithium stored for use in the next battery discharge cycle. Thus, each discharge and charge event is considered to be a cycle in which lithium ions are between the positive electrode 24 and the negative electrode 22 to move back and fourth.

The one for charging the battery 20 External power source used may vary in size, construction, and the particular end use of the battery 20 vary. Some noteworthy and exemplary external sources include, but are not limited to, an AC wall outlet and an automotive alternator. In many lithium-ion, lithium-sulfur, and lithium-selenium battery configurations, the negative current collector becomes 32 , the negative electrode 22 , the separator 26 , the positive electrode 24 and the positive pantograph 34 each made as relatively thin layers (e.g., from a few microns to a millimeter or less in thickness) and assembled into layers which are connected in electrical parallel connection to provide a suitable energy package.

Furthermore, the battery 20 include a variety of other components which, although not shown here, are well known to experts. For example, the battery 20 a housing, seals, terminal caps, tabs, battery terminals, and any other conventional components or materials that may be contained within the battery 20 including between or around the negative electrode 22 , the positive electrode 24 and / or the separator 26 can. As mentioned above, the size and shape of the battery 20 vary depending on the particular application for which it is designed. Battery-powered vehicles and portable consumer electronics are two examples where the battery 20 probably would have a different size, capacity and power output. The battery 20 may also be connected in series or in parallel with other, similar lithium-ion cells or batteries to provide greater voltage output, power, and power, if that is to the consumer 42 is required.

Accordingly, the battery 20 electric power to a consumer 42 generate, which is operative with the external circuit 40 can be connected. While the consumer device 42 may be any number of electrically driven devices, some specific examples of power consuming consumer devices include an electric motor for a hybrid vehicle or for a fully electric vehicle, a laptop computer, a tablet computer, a mobile phone, and a cordless power tool or home appliances. The consumer device 42 However, it may also be a power generating device that the battery 20 loads to save energy. In some other variations, the electrochemical cell may be a supercapacitor, such as a lithium ion-based supercapacitor.

Referring again to 1 can the positive electrode 24 , the negative electrode 22 and the separator 26 one electrolyte solution or one system each 30 include the lithium ions between the negative electrode 22 and the positive electrode 24 can guide. The electrolyte system 30 may have a viscosity in the range of about 50 mPa.s to about 500 mPa.s. In certain aspects, the electrolyte may 30 an anhydrous liquid electrolyte solution containing one or more lithium salts dissolved in an organic solvent or a mixture of organic solvents. In certain variations, the electrolyte can 30 a 1M solution of one or more lithium salts in one or more organic solvents. Many conventional nonaqueous liquid electrolyte solutions can be used in the lithium ion battery 20 be used.

A non-limiting list of lithium salts that can be dissolved in an organic solvent to form the nonaqueous liquid electrolyte solution includes lithium hexafluorophosphate (LiPF ₆ ); Lithium perchlorate (LiClO ₄ ); Lithium tetrachloroaluminate (LiAlCl ₄ ); Lithium iodide (LiI); Lithium bromide (LiBr); Lithium thiocyanate (LiSCN); Lithium tetrafluoroborate (LiBF ₄ ); Lithium tetraphenylborate (LiB (C ₆ H ₅ ) ₄ ); Lithium bis (oxalate) borate (LiB (C ₂ O ₄ ) ₂ ) (LiBOB); Lithium difluorooxalatoborate (LiBF ₂ (C ₂ O ₄ )), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium trifluoromethanesulfonimide (LiN (CF ₃ SO ₂ ) ₂ ), lithium bis (fluorosulfonyl) imide (LiN (FSO ₂ ) ₂ ) (LiSFI) and combinations thereof.

These and other similar lithium salts can be used in a variety of organic solvents, including, but not limited to, various alkylcarbonates such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC)). ), linear carbonates (eg, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), aliphatic carboxylic acid esters (eg, methyl formate, methyl acetate, methyl propionate), γ-lactones (eg) , γ-butyrolactone, γ-valerolactone), chain structure ethers (e.g., 1,2-dimethoxyethane, 1-2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), 1.3 Dioxolane and combinations thereof.

In various aspects, the positive electrode 24 are formed from a lithium-based active material which is sufficiently capable of intercalation and disintercalation, alloying and delegation or coating and stripping of lithium when used as the positive pole of the battery 20 serves. The electroactive materials of the positive electrode 24 may include one or more transition metals such as manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V) and combinations thereof. Two exemplary common classes of known electroactive materials used to form the positive electrode 24 can be used, are layered lithium transition metal oxides and spinel phase lithium transition metal oxides.

For example, the positive electrode 24 in certain cases, include a spinel type transition metal oxide, such as lithium manganese oxide (Li _{(1 + x} ) Mn _(2-x) O ₄ ), where x is typically less than 0.15, including LiMn ₂ O ₄ (LMO) and lithium manganese. Nickel oxide LiMn _1.5 Ni _0.5 O ₄ (LMNO). In certain cases, the positive electrode 24 Layered materials such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium nickel manganese cobalt oxide (Li (Ni _x Mn _y Co _z ) O ₂ ), where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z = 1, including LiMn _0.33 Ni _0.33 Co _0.33 O ₂ , a lithium nickel cobalt metal oxide ( _{(1-xy )} Co _x M _y O _2), where 0 <x <1, 0 <y <1, and M is Al, Mn or the like can. Other known lithium transition metal compounds such as lithium iron phosphate (LiFePO ₄ ) or lithium iron fluorophosphate (Li ₂ FePO ₄ F) can also be used. In certain aspects, the positive electrode may be 24 an electroactive material including manganese such as lithium manganese oxide (Li _{(1 + x)} Mn _(2-x) O ₄ ), a mixed lithium manganese nickel oxide (LiMn _(2-x) Ni _x O ₄ ) wherein 0 ≤ x ≦ 1, and / or a lithium manganese nickel cobalt oxide (e.g., LiMn _1/3 Ni _1/3 Co _1/3 O ₂ ). In a lithium-sulfur battery, positive electrodes may include elemental sulfur as the active material or a sulfur-containing active material.

In certain variations, these positive active materials may be mixed with an optional electrically conductive material and at least one polymeric binder material to structurally reinforce the lithium based active material along with optional electrically conductive particles dispersed therein. For example, the active materials and optional conductive materials with such binders as polyvinylidene difluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene-propylene-diene monomer (EPDM) rubber or carboxymethylcellulose (CMC), nitrile-butadiene rubber ( NBR), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate. Electrically conductive materials can include graphite, carbonaceous materials, nickel powder, metal particles, or a conductive polymer. Carbonaceous materials may by way of non-limiting example include KETCHENTM ™ carbon black, DENKATM ™ carbon black, acetylene black, carbon black, and the like. Examples of a conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole and the like. In certain aspects, mixtures of conductive materials may be used. As mentioned above, a positive electrode current collector 34 at or near the positive electrode 24 be positioned. The positive pantograph 34 may be made of aluminum (Al) or any other suitable electrically conductive material.

According to various aspects, the negative electrode contains 22 an electroactive material as a lithium host material that can serve as a negative terminal of a lithium ion battery. The negative electrode 22 Thus, it may include the electroactive lithium host material and optionally another electrically conductive material and one or more polymeric binding materials for constructively holding the lithium host material together. The negative electrode 22 may comprise greater than about 50% to less than about 100% of the electroactive material, optionally less than about 30% of an electrically conductive material, and a balance binder.

For example, the negative electrode 22 in certain cases, comprise the electroactive material which mixes with a binder material selected from the group consisting of: polyvinylidene difluoride (PVDF), ethylene-propylene-diene monomer (EPDM) rubber or carboxymethyl cellulose (CMC), a nitrile butadiene rubber Rubber (NBR), styrene-butadiene rubber (SBR), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, polyimide and combinations thereof. Suitable additional electrically conductive materials may include carbonaceous materials or a conductive polymer. Carbonaceous materials may include, for example, KETCHENTM ™ carbon black, DENKATM ™ carbon black, acetylene black, carbon black, and the like. Examples of a conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole and the like. In certain aspects, mixtures of conductive materials may be used. As mentioned above, a negative electrode current collector 32 at or near the negative electrode 22 be positioned. The pantograph 32 may comprise a metal selected from the group consisting of: copper, nickel, iron, titanium, and combinations thereof. The pantograph can For example, be formed from an iron alloy, such as stainless steel.

In various aspects, the porous separator 26 a microporous polymeric separator containing a polyolefin. The polyolefin may be a homopolymer (derived from a single monomer component) or a heteropolymer (derived from more than one monomer component), which may be either linear or branched. When a heteropolymer is derived from two monomer constituents, the polyolefin may take any copolymer chain arrangement including those of a block copolymer or a random copolymer. Likewise, a polyolefin which is a heteropolymer derived from more than two monomeric constituents may also be a block copolymer or a random copolymer. In certain aspects, the polyolefin may be polyethylene (PE), polypropylene (PP) or a blend of polyethylene (PE) and polypropylene (PP) or multilayer structured porous films of polyethylene (PE) and / or polypropylene (PP).

When the porous separator 26 Being a microporous polymeric separator, it may be a single layer or a multi-layered laminate made by either a dry or a wet process. For example, in one embodiment, a single layer of the polyolefin may comprise the entire microporous polymeric separator 26 form. In other aspects, the separator 26 a fibrous membrane having a plethora of pores extending between opposing surfaces and may, for example, have a thickness of less than one millimeter. As another example, the microporous polymeric separator 26 but also composed of several separate layers of the same or a non-similar polyolefin.

In different aspects, like in 2 to see includes the separator 100 a doped substrate 102 and a cover layer disposed thereon 104 , In various cases, the substrate comprises 102 a dopant 106 selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tin oxide (SnO), silicon oxide (SiO ₂ ), Tantalum oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), hydrofluoroolefin (HfO), cerium oxide (CeO ₂ ), and combinations thereof. The doped substrate 102 may be an amount of dopant ranging from about 1 g / m ² to about 10 g / m ² , optionally from about 2 g / m ² to about 5 g / m ² and, in certain aspects, optionally from about 4 g / m ² to about 5 g / m ² . The doped substrate 102 may have a porosity in the range of about 30 Gurley seconds to about 40 Gurley seconds, and in certain aspects optionally 31 Gurley seconds. The doped substrate 102 may have a thickness in the range of about 15 microns to about 20 microns.

In different cases, the topcoat 104 one of a polymeric capping layer and a ceramic metal oxide coating. The ceramic metal oxide cap layer comprises a ceramic material selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), silica (SiO ₂ ), and combinations thereof , The ceramic metal oxide capping layer may be deposited on the doped separator by atomic layer deposition (ALD). The polymeric capping layer may comprise one of an aluminum oxide composite (Alukon) film, a zirconium alkoxide composite (zirconium) film, a titanium alkoxide composite (Titanicon) film, and a polyimide film, and may be disposed on the doped separator by means of molecular layer deposition (MLD). Thus, the cover layer 104 in various aspects comprise a compound selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tin oxide (SnO ), Silica (SiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), hydrofluoroolefin (HfO), ceria (CeO ₂ ), and combinations thereof. The overcoat layer may have a thickness in the range of about 1 nm to about 50 nm, optionally from about 1 nm to about 10 nm, and in certain aspects optionally from about 2 nm to about 10 nm.

In certain aspects, the modified separator 100 containing a doped substrate 102 and the topcoat disposed thereon 104 comprises improved wettability over the relatively high-viscosity electrolyte (eg, the electrolyte system 30 ) while blocking dendritic formation. Thus, the long-term performance of the electrochemical cell (eg, the battery 20 ), such as a lithium metal based battery, including the modified separator. 3 shows, for example, the charge and discharge profiles of the comparative electrochemical cells 200 . 202 . 204 and 206 each containing an electrolyte system having a viscosity ranging from about 50 mPas to about 500 mPas and a polypropylene-based separator. Y ₁ -axis 210 represents capacity conservation in milliampere-hours (mAh) while the cycle number is plotted on x-axis 212. The y ₂ -axis 214 represents the efficiency.

The electrochemical cell 200 includes a baseline separator comprising pure polypropylene and an electrolyte system having a viscosity of about 100 mPa · s. The electrochemical cell 202 includes a separator comprising a polypropylene substrate coated with a topcoat comprising Al ₂ O ₃ and having an electrolyte system having a viscosity of about 100 mPa · s. The electrochemical cell 204 includes a separator comprising a polypropylene substrate with an SiO ₂ dopant in an amount of about 2 g / m ² to about 5 g / m ² and with an electrolyte system having a viscosity of about 100 mPa · s. The electrochemical cell 206 includes a separator prepared in accordance with certain aspects of the present disclosure. In particular, the electrochemical cell includes 206 the dopant of the electrochemical cell 204 and the coating of the electrochemical cell 202 and has an electrolyte system with a viscosity of about 100 mPa · s. As you can see, the electrochemical cell 206 towards the electrochemical cells 200 . 202 and 204 a significantly improved long-term performance and stability. Accordingly, the electrochemical cell 206 In accordance with certain aspects of the present disclosure, the invention has improved cycle performance and reduced capacity degradation.

In various aspects, the present disclosure provides a method of forming the overcoat of the modified separator. In various aspects, the method includes applying one of a polymeric overcoat and a ceramic metal oxide overcoat to a doped separator. In certain aspects, the polymeric topcoat may be applied by, for example, molecular layer deposition (MLD). The polymeric overcoat resulting from molecular layer deposition (MLD) may include an alumina composite (Alukon) film, a zirconium alkoxide composite (zirconium) film, a titanium alkoxide composite (Titanicon) film, and a polyimide film include. For example, the polymeric overcoat may be an alumina composite (Alukon) film resulting from a precursor material selected from the group consisting of: trimethylaluminum (TMA), ethylene glycol (EG), terephthaloyl chloride (TC), glycidol (GLY), hydroquinone (HQ) and combinations thereof.

In certain aspects, the ceramic metal oxide capping layer may be deposited, for example, by atomic layer deposition (ALD). The ceramic metal oxide cap layer resulting from atomic layer deposition (ALD) may comprise a ceramic material selected from the group consisting of: alumina (Al ₂ O ₃ ); Titanium dioxide (TiO ₂ ); Zirconia (ZrO ₂ ); Zinc oxide (ZnO); Silicon oxide (SiO ₂ ) and combinations thereof and is disposed on the doped separator using atomic layer deposition (ALD).

The foregoing description of the embodiments is merely illustrative and descriptive. It is not meant to be exhaustive and is not intended to limit revelation in any way. Individual elements or features of a particular embodiment are generally not limited to this particular embodiment, but may be interchangeable and optionally usable in a selected embodiment, although not separately illustrated or described. Also various variations are conceivable. These variations are not deviations from the disclosure, and all modifications of this nature are part of the disclosure and are within its scope.

Claims (10)

A modified separator for an electrochemical cell that recycles lithium ions, the modified separator comprising: a polymeric separator comprising a doped substrate and a cover layer disposed thereon, wherein the substrate is doped with a dopant selected from the group consisting of: alumina (Al ₂ O ₃ ), titanium dioxide (TiO ₂ ), zirconium dioxide (ZrO ₂ ), zinc oxide (ZnO), iron oxide (Fe ₂ O ₃ ), tin oxide (SnO), silicon oxide (SiO ₂ ), tantalum oxide (Ta ₂ O ₅ ) , Lanthanum oxide (La ₂ O ₃ ), hydrofluoroolefin (HfO), ceria (CeO ₂ ), and combinations thereof, and the overcoat layer is one of a polymeric overcoat and a ceramic metal oxide overcoat, wherein the ceramic metal oxide doping comprises at least one of the dopants includes; and an electrolyte system having a viscosity in the range of about 50 mPas to about 500 mPas. Modified separator after Claim 1 wherein the cover layer has a thickness in the range of about 1 nm to about 50 nm. Modified separator after Claim 2 wherein the polymeric overcoat comprising a film of an alumina composite (Alukon) film, a zirconium alkoxide composite (zirconium) film, a titanium alkoxide composite (titanicon) film, and a polyimide film. Modified separator after Claim 3 wherein the polymeric overcoat is the aluminum oxide composite (Alukon) film comprising a precursor material selected from the group consisting of: trimethylaluminum (TMA), ethylene glycol (EG), terephthaloyl chloride (TC), glycidol (GLY), hydroquinone (HQ) and combinations thereof. Modified separator after Claim 4 wherein the modified separator has a melting point in the range of about 120 ° C to about 200 ° C and the precursor material includes a combination of trimethylaluminum (TMA) and ethylene glycol (EG). Modified separator after Claim 4 wherein the electrolyte system is one of an ether-based electrolyte system and a carbonate-based electrolyte system. Modified separator after Claim 3 wherein the polymeric coating is a molecular layer deposition (MLD) topcoat. Modified separator after Claim 7 wherein the ceramic metal oxide cap layer comprises a ceramic material selected from the group consisting of: alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), zinc oxide (ZnO), silica (SiO ₂ ) and Combinations thereof. Modified separator after Claim 8 wherein the ceramic metal oxide coating is an atomic layer deposition (ALD) capping layer. Modified separator after Claim 1 wherein the substrate comprises: an amount of a dopant ranging from about 1 g / m ² to about 10 g / m ² ; and a polyolefin.

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